Some homes and businesses employ hydronic (water-based) or other fluid heating systems to heat living spaces, pools, spas, walkways, driveways, hot water for washing, etc., or for process heat. Fluid heating systems distribute heated fluid through a series of heat exchanging pipes that are positioned throughout the heating loads. Conventional hydronic systems use on-demand sources, such as boilers and chillers, to thermally adjust fluids that circulate throughout the system.
In fluid heating and cooling systems it is desirable to measure the heat energy transferred into and out of each heat source and load. Measuring and monitoring heat transfer from a fluid system is necessary for receiving financial rebates, such as renewable energy credits, as well as for controlling the various heat sources and loads.
For fluid systems having multiple heat sources and loads, measuring and monitoring heat energy transfer from each of the heat sources and loads may be expensive. In particular, because available energy meters, such as a British Thermal Unit (BTU) meters, need to be affixed to the fluid system at each measurement point, for example, at each heat source or load, a system may often include several expensive BTU meters.
In general, a BTU meter includes a flow meter and a temperature sensor, the data from which are combined according to mathematical formula to determine the heat energy transfer from a particular heat source or load. The flow meter component of the BTU meter is expensive, with the temperature sensors being a comparably inexpensive component. In particular, a current fluid system having three heat loads requires three expensive flow meters and six thermistors to accurately measure the heat consumption of each load.
Therefore, what is needed is an effective and cost efficient heat energy measurement system that reduces the number of flow meters in the system without losing measurement accuracy.